1. Field of Industrial Application
The present invention relates to galactosamine substitutes of poly-.omega.-substituted-L-glutamic acid (or aspartic acid) which are useful as high molecular materials for medical use, especially as missile drug carriers.
2. Prior Art
In glycoprotein in serum, a sugar structure called sialic acid-galactose-N-acetylglucosamine is omnipresent at the termini thereof. In the late 1960's, G. Ashwell and A. Morell clarified that this triose structure was required for serum protein to be stably present in blood. When sialic acid which is present at the termini is eliminated, galactose becomes a new sugar end. Glycoprotein from which the sialic acid has been removed so that galactose has been exposed is called asialo glycoprotein. Asialo glycoprotein cannot be stably present in blood flow and rapidly disappears from blood. It is revealed that more than about 80% of the asialo glycoprotein is taken up into liver.
Specific sugar recognition receptors are present on the surface of the membrane in hepatocytes. Asialo glycoprotein is taken up into cells via this asialo glycoprotein receptor. The present inventors have made investigations, paying attention to this asialo glycoprotein receptor on the hepatocytes membrane, directed towards developing high molecular materials for drug carriers used in missile drugs, etc. As a result, it has been found that polyamino acids in which galactosamine has been introduced as a sugar residue have excellent properties. The present invention has thus been accomplished.